Wall Street asks: Why can't Nasdaq get it right?

After the Nasdaq exchange shut down trading for an unprecedented three hours today, many voices on Wall Street were wondering: Why can't Nasdaq get its act together?

Reuters reported that 30 minutes into the outage that hobbled the Nasdaq stock market Thursday afternoon, exchange officials already had the problem fixed. But amid caution, it took another two-and-a-half hours before it was ready to turn the all-electronic market back on.

Former Securities and Exchange Commission Chairman Harvey Pitt told CNBC that the Nasdaq's performance was "inexcusable."

"Nasdaq has, in my view, serious issues, and there are two particular problems here," he said. "The first is, is their technology up to the task? ... The second is that when technology goes bad, do they have an established crisis management program?

"I think the problem is requiring the use of technology to be continuously tested and updated. Testing will start to reveal problems. It won't catch all of them, but it is required now to have a continuous stream of testing—and not once every quarter or once every half year," Pitt said.

At the close of trading, the Nasdaq still hadn't explained what happened.

"It seems as if computer glitches are happening with more frequency, and it may be due to human error on the programming side," said Marc Lasry at Avenue Capital. "We have to decide if we are comfortable with the risk that these glitches can close markets."

Dennis Gartman, author of The Gartman Letter and a frequent CNBC contributor, called the outage an "embarrassment."

"This is such an embarrassment to the entire financial community. To have the Nasdaq go down as it has; to be down three hours—it's one thing to be down for five minutes—to be down for three hours is absolutely inexcusable," he said.

Another investor told CNBC, "This is a lot less serious on a Thursday afternoon in August than it would be at some other time. It will affect people who really need liquidity and were planning to get it from Nasdaq stocks. These things happen nowadays, markets break down. It's an assumed risk of trading that the market you need to trade in could break down."